1. Field of the Invention
The invention relates to an on-board warning apparatus and warning method for warning a driver using results from measuring the time for which the driver is inattentive and the time for which the driver is dozing off or the time for which the drive's eyes are closed.
2. Description of the Related Art
Japanese Patent Application Publication No. 2002-219968 (JP-A-2002-219968), for example, describes a warning apparatus that issues a warning when a driver is inattentive or dozing off while driving. This warning apparatus includes driver state detecting means for detecting an inattentive state and a dozing state of the driver; measuring means for measuring the duration of the inattentive state and the dozing state of the driver; vehicle speed detecting means for detecting the vehicle speed; vehicle-to-vehicle distance detecting means for detecting the distance to a leading vehicle; vehicle-to-vehicle time calculating means for calculating the time to the leading vehicle based on the vehicle speed detection value and the vehicle-to-vehicle distance detection value; allowable time setting means for looking up and setting an allowable time corresponding to the vehicle-to-vehicle time calculating value from a table listing allowable times with respect to vehicle-to-vehicle times set beforehand so that the allowable time is the maximum value at a predetermined vehicle-to-vehicle time; and determining means for determining that the driver is inattentive or dozing off while driving when the duration of the inattentive state or the dozing state exceeds the allowable time set value.
Also, Japanese Patent No. 2583335, for example, describes a leading vehicle approaching warning apparatus that includes host-vehicle vehicle speed detecting means for detecting the driving speed of a host vehicle; leading-vehicle vehicle speed detecting means for detecting the driving speed of a leading vehicle; vehicle-to-vehicle distance detecting means for detecting the vehicle-to-vehicle distance between the host vehicle and the leading vehicle; warning issuing means for issuing a warning to the driver when the relative speed of the host vehicle with respect to the leading vehicle becomes equal to or greater than a predetermined allowable relative speed, with respect to the vehicle-to-vehicle distance; and driving state detecting means for detecting when the driver is inattentive or dozing off while driving. This leading vehicle approaching warning apparatus corrects, i.e., lowers, the allowable relative speed when inattentiveness or dozing off while driving is detected, and issues the warning when the relative speed of the host vehicle becomes equal to or greater than that corrected allowable relative speed.
In the invention described in JP-A-2002-219968, the allowable time set value with respect to the duration of the inattentive state or the duration of the dozing state is set according to the vehicle-to-vehicle time. Therefore, the allowable time set value with respect to the duration of the inattentive state and the allowable time set value with respect to the duration of the dozing state are the same values. However, the inattentive state and the dozing state each have different characteristics so the warning timing may not be appropriate with a structure that sets the warning timing with the same determining reference for the inattentive state as it does for the dozing state.
Also, similarly, in the invention described in Japanese Patent No. 2583335, the warning timing when there is a danger of collision is set without taking the respective characteristics of the inattentive state and the dozing state into account so the warning timing may not be appropriate.